Right class,
now it's time we got down to some serious learning. I know; learning is boring,
but in this case understanding the science can help us make gains in the gym.
Science classically is the domain of the scrawny nerd but no longer! Now the
bulky bodybuilder can benefit from its dark secrets and fight back! This is
learning with real-world benefits, unlike PSE or Maths at school. So pay
attention! There might be a test at the end. Really.
We all know if we have a 'fast' or 'slow' metabolism, but do we know what one
is? I do. 'Metabolism' refers to the chemical reactions that take place to
supply our body with energy (catabolism) and to build and repair tissue with
proteins (anabolism) by acting out our DNA code. Here we're going to discuss
what that means for bodybuilding.

Muscle Tissue

Skeletal muscle tissue is the largest organ in the human body and makes up over
a third of body mass in healthy adults.
Muscle tissue, like every other part of the body, is formed from millions of
tiny cells. In muscle they are cleverly named 'muscle fibres'. Unlike other
cells these have multiple nuclei (the command centre of a cell) meaning that
they cannot multiply through mitosis (cell division). Muscle fibres are
composed of smaller 'strands' named myofibrils, which in turn are made of
sarcomeres. Inside Sarcomeres are smaller filaments made from the proteins
myosin and actin. When the muscle contracts, this is an effect of the myosin
'pedaling' along the actin and so collapsing the sarcomeres inwards like
collapsable tubes. As enough of them do it this becomes visible on a
macroscopic level and moves your entire arm.

Following so far? I'm not sure I am. Just to complicate matters there are
actually 2 different types of muscle fibre; 'fast twitch' and 'slow twitch'
(also known as type I and type II). As the names suggest, fast twitch fibres
are used in fast explosive movements such as jumping, sprinting and
weightlifting, while slow twitch fibres are used for endurance sports such as
long-distance running. The difference is due to the amounts of mitochondria,
creatine phosphate among other things in the fibres, as well as the myosin
isoforms, and we will see how these effect performance later on. Basically it
comes down to how quickly/efficiently they get energy from ATP.
Type II can be further divided into Type IIa and Type IIx with the latter being
even faster. Certain mamals have another kind of fibre, 'Type IIb' which is
used for even more sudden bursts of energy used to change direction suddenly
and evade predators (confusingly you will sometimes find Type IIb referred to
as Type IIx and vice versa - while most websites and magazines still refer to
humans' fastest fibre as Type IIb most scientific journals and papers have now
adopted IIx). Generally a bodybuilder will have more Type II fibres, as will
sprinters, long distance runners will need more Type I. While our ratio of
fast-twitch to slow-twitch fibres is larlgey genetically determined studies
have shown that we are able to convert one type of muscle fibre into another
through training. There are also muscle fibres that are 'in-betweenies' with
aspects of both fast twitch and slow twitch fibres. As we get older up to a
third of our muscles become 'in betweenies'.

Energy

Muscles get energy from splitting ATP (Adenosine Triphosphate: an adenine
nucleotide that's bound to three phosphates), the 'universal energy currency'
of life. ATP is produced in the mitochondria of cells from the glucose in our
diet and energy is released when the high-energy bonds are broken releasing the
phosphate.
Creatine phosphate is used to restore the levels of ATP by converting used ATP,
or ADP (Adenosine Diphosphate - an adenine nucleotide with two phosphates (AMP
has one)), back into ATP using its own high-energy phosphate bond. This
supplies our muscles with energy during fast usage such as during sprinting
(the phosphogen system). Our muscles can only store enough ATP for roughly 3
seconds use at full power, but fortunately they can store around 2-3 times more
creatine phosphate allowing for 8-10 seconds of exertion at full pelt. This is
why bodybuilders use creatine supplements - to supply the muscle with more
energy. This is called the Phosphogen System.
ATP can also be obtained from the carbohydrate glycogen, though it is a
slightly slower process, in what's called the Glycogen Lactic Acid System. Here
glycogen stored in the muscles is split into glucose which is split further
releasing four ATP molecules. This provides roughly 1.5 minutes of extra energy
on top of the initil 8 seconds, although at lower power and also produces the
bi-product lactic acid. This method is used in activities such as swimming or
the 400 metre sprint and is 'anaerobic' meaning it does not use oxygen.
Finally the Aerobic System is used to maintain a supply of energy for extended
use. It achieved this through the oxydisation of foodstuffs in our
mitochondria. The system will 'burn' carbohydrates first, then fats and finally
protein to supply the body with a source of energy. This is why bodybuilders
should not engage in excessive CV or completely neglect Carbohydrates in their
diet - they will risk canabalising their protein. The Aerobic system can
sustain an athlete for over two hours, and converts glucose into carbon dioxide
and water rather than lactic acid. In order to provide muscles with the
necesary oxygen your body will pump blood to them (hence the feeling of being
'pumped'), diverting it from other organs, and increase the depth and rate of
your breathing. Oxygen is carried in the blood in hemoglobin and in the muscles
is stored in protein molecules called myoglobin.
These three systems kick in in sequence, begining with the Phosphogen System,
then moving onto the Glycogen Lactic Acid System and finally the Aerobic System
if exertion continues.

Muscle Growth

As stated earlier - muscle fibres cannot reproduce via mitosis due to their
multiple nuclei. This means that in order for the muscle to get bigger, the
existing fibres to become thicker. To do this the muscle must add more
myofibrils which it does via their longitudinal splitting. This action however
requires allot of Myosin, Actin and other proteins. The amount of protein that
your muscle fibres can use is limited by the number of nuclei for each one.
When you strain a muscle from overloading you creating 'microtears' in the fibres.
Don't worry though, this is how hypertrophy (or 'muscle-getting-bigger-ness')
occurs. Once the fibre is recognised as damage you see, 'satellite cells' (AKA
stem cells, ones which hang around ready to jump to action) will fly on over in
order to repair the damage (in little cell-planes I like to believe). The
single nuclei of the satelite cells however will stick around and become
incorporated into the repaired fibre meaning that it has more nuclei than it
did before and can use more proteins to become thicker.

6. Which two proteins make up the tiny filaments in our muscle fibre?
a. Myosin and Actin
b. Hemoglobin and Actin
c. Myosin and myofibrils
d. Sarcomeres and muscle fibres

Answers: c, b, c, b, a, a

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